The primary design this page refers to as D4 has so far only appeared in the 2006Ships of the Line Calendar and Ships of the Linebook. The design was created by Robert Bonchune, intended to be used in the Enterprise episode Unexpected, unfortunately as the production team had been over worked on the earliest Enterprise episodes they did not have time to make the model and a K't'inga class was used instead. Later appearances by the Klingons only featured specifically Enterprise era designs and Bonchune did eventually make a model of the D4, but it did not make an appearance on screen.

Before Enterprise even existed the D4 class had been referred to in the novel The Final Reflection where until the early 23rd century it made up most of the Klingon fleet, unlike in Enterprise the D5 class was not contemporaneous of the D4 but was a new 23rd century design which eventually supplanted the D4.

The game Legacy also features a D4 class, an Enterprise era vessel but not the Bonchune design, this type of D4 is also known as the Predator class in the game.